The present invention relates to protective covers and pertains particularly to a protective cap or guard for threaded pipe and tubing.
Threaded pipe and tubing generally requires a protective cover over the threaded ends to prevent damage to the threads during handling and shipping. This is particularly critical for precision pipe fitting and tubing such as that utilized for oil field use.
Various protective covers and caps are available for use on pipes and tubings. Those caps and protective covers presently available, however, are not satisfactory for preshipment handling during the manufacturing and testing process. Such caps that are currently available are either threaded onto the pipe and require threaded removal or in the alternative require at least threaded removal. Such removal by unscrewing the cap from the threads is time consuming and adds considerably to the costs of production because of the delays which it causes in the production line.
Oil well tubing and casing in the form of seamless pipe must be accurately manufactured. The manufacturing, threading, gauging and inspection of such casing and tubing is rigidly controlled by the American Petroleum Institute. In high speed tubing and casing manufacturing, the steel pipe rolls down a production line and a pipe is threaded every twenty seconds. Hourly employees stand at the threader and inspect every fifth pipe for quality control. So few are checked as there is little time and also because of the precise capabilities of the threading machine which rarely produces a quality control problem.
After the threading is completed, the pipes roll into a cradle for removal into a high pressure testing area. At the high pressure testing area, the pipe is again placed on a gently tilted runout table that tilts toward the tester. At the tester, steel couplers are threaded onto the pipe and the pipe is subjected to 10,000 psi of water pressure to check the integrity of the pipe and the threaded ends. After completion of the threading operation, up to 2% losses are usually suffered primarily because of thread damage. While the pipe can usually be rethreaded once, it is scrapped if damage occurs more than once. The damage usually occurs in the handling of the pipe. The drop from the runout table and the storage area are major contributors to the thread damage.
Other damage occurs as a result of tubing lengths. Oil tubing is upset and has a plug collar which is actually larger than the tubing itself. Any misalignment in the stacks of the tubing or different lengths result in the plug collars of one pipe engaging and damaging the threads on the adjacent pipe.
One major consideration in solving this problem is the time factor in installing and removing the thread protective caps or guards. Threaded protectors that are available in the form of threaded sleeves reduces the production rate by nearly 50%, so that the cure is actually more expensive than the damage problem itself.
It is therefore desirable that an improved thread guard or protective cap be available.